The incidence of spinal cord injury (SCI) in the United States is approximately 11,000 per year, with a prevalence of about 250,000 incidents. Damage to the spinal cord interrupts motor commands to the muscles and internal organs, resulting in loss of ambulation and damage to autonomic functions. Approximately 52% of this population have motor incomplete lesions and therefore have the potential to regain functional ambulation. One of the primary goals of individuals with SCI is to regain the ability to walk. Restoration of independent ambulation is a major focus of rehabilitation in incomplete SCI (iSCI).
Currently, therapist-assisted, body-weight-supported treadmill training (BWSTT) is used for rehabilitation of many SCI patients. This is accomplished by making the patient walk on a motorized treadmill with a counter-weight harness system, while therapists aid the patient by manually moving the legs and trunk. Clinical trials of locomotor training in iSCI patients indicate improvements in walking. The use of BWSTT simply increases the safety and convenience of gait training. Despite these benefits, clinical practice of BWSTT is limited because of the requirement of at least three therapists to provide manual facilitation of appropriate stepping kinematics. Also, the duration of such training may be limited by therapist fatigue.
Various motorized (robotic) devices have been developed for rehabilitation of lower limbs. Using robotic assisted BWSTT in conjunction with body weight support (BWS), researchers have showed that significant improvements can be achieved in the walking ability of patients with chronic and sub-acute SCI. The cost of such a device makes it prohibitive for many facilities, however, which limits accessibility of step training for iSCI-inflicted individuals having geographic and/or socioeconomic barriers. Also, improvement is limited in many robotic locomotor devices because they provide assistance by moving the limbs through pre-determined kinematic patterns independent of voluntary effort.
To increase the accessibility of BWSTT, financial and physical costs should be minimized and voluntary activity should be maximized. Non-motorized devices have been developed to assist extremity movements by eliminating or reducing the effects of gravity, such as the gravity-balanced orthosis described in U.S. patent application Ser. No. 11/113,729 (hereinafter “the '729 application”), filed Apr. 25, 2005, and assigned to the assignee of the present invention, incorporated herein by reference. There is still a need in the art, however, for apparatus that offer improved assistance to the limbs or trunk of a user during BWSTT to maximize voluntary motor activity during gait training required for recovery of independent ambulation.